The effects of ligand modification on the catalytic mechanism of hydrogen production by Ni(PyS)₃^– derivatives, made with electron-withdrawing and -donating substitutions to the pyridinethiolate (PyS)⁻ ligands, are studied experimentally and computationally using density functional theory. Thermodynamic data, spin density maps, and frontier molecular orbital diagrams were generated for reaction intermediates. Comparison of computed values for E⁰ and pK_a with experimental values supports the proposed mechanisms. The rate of electrochemical hydrogen production is correlated with the effect of ligand modification. Notably, the presence of an electron-donating substituent favors an alternative mechanism for hydrogen production. Computationally it was determined that the electron-donating substituent causes deviation from the original chemical–electrochemical–chemical–electrochemical (CECE) mechanism of Ni(PyS)₃^– to a CCEE mechanism, while the CECE mechanism is maintained for all catalysts substituted with electron-withdrawing groups.

中文翻译：

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配位基修饰的对电制氢用Ni（基吡啶）机制₃ ^-衍生物

配体修饰对用Ni（PYS）制氢的催化机制的影响₃ ^-衍生物，具有吸电子和-donating取代的基吡啶（PYS）制成^-配体，进行了研究和实验计算使用密度泛函理论。生成了反应中间体的热力学数据，自旋密度图和前沿分子轨道图。E ⁰和p K _a的计算值比较实验值支持所提出的机制。电化学氢产生的速率与配体修饰的作用相关。值得注意的是，给电子取代基的存在有利于产生氢的另一种机理。计算它被确定给电子取代基会导致偏差选自Ni（PYS）的原始化学电化学化学电化学（CECE）机构₃ ^-至CCEE机构，而CECE机构维持用于与电子取代所有催化剂-撤军团体。